CNET reader "deesmac" asks:
Why doesn't a DVD recorder have an HDMI in, as well as an HDMI out?
It's a great question. High-Definition Multimedia Interface provides the advantage of passing a high-bandwidth all-digital high-definition video and audio signal on a single cable, as opposed to the tangle of component video plus audio cables that were required for HD. (If those terms are Greek to you, check out the connectivity section of the CNET TV Buying Guide.) HDMI is now the standard connector for HDTVs and all of the HD-capable components that connect to them--DVD players and recorders, DVRs, game consoles, Blu-ray and HD DVD players, and even camcorders and PCs. But all of those are video sources that only have HDMI outputs. You'll find HDMI inputs only on AV receivers, HDMI switchers, and--of course--TVs. So, why the disparity?
Not surprisingly, the dearth of HDMI inputs on recording devices is by design. The HDMI specification includes a copy-protection scheme known as High-Definition Copy Protection. So to use HDMI (and get the snazzy HDMI certification logo on your device), manufacturers need to ensure that their products are HDCP-compliant. That pretty much means that HDMI inputs are limited to display devices (TVs) and repeaters (AV receivers and switchers). Those repeaters are so-called "passthrough" devices--they can do little more than pass the HD video signal onto the next device (invariably, the TV). But, by definition, that HDCP-encoded video signal is designed to be unrecordable. That's why there are no recorders with an HDMI input. (You won't find HDMI inputs on Slingbox products for the same reason.)
So what's the alternative? Recorders with component video inputs are few and far between: Philips had component-in on its otherwise lackluster DVD recorders in years past, as did Sony on at least one model--but both companies have since dropped the feature. The upcoming Hauppauge video encoder supposedly can accept and process 1080p video via its component inputs. Likewise, several Slingbox models (as well as competing placeshifting products from Sony, Monsoon/HAVA, and Pinnacle) can accept component video--including HD streams--and pass it through to a TV or AV receiver. However, for recording you're pretty much stuck either with "closed box" HD DVRs or utilizing the so-called analog hole: the composite or S-Video output from your DVR, cable, or satellite box will still output an analog video signal--not in high-definition, of course--that's easily recordable. Which is why they're the only two inputs you'll find on your DVD recorder. (Speaking of which: make sure you use S-Video in--the quality is noticeably better than composite.)
The irony here, as usual, is that honest users who just want more convenience, better quality, and fewer wires are the losers--even as digital piracy remains as rampant as ever (thanks to PC-based recording, not set-top recorders). Still, don't expect Hollywood studios or electronics manufacturers to change their tune on this one. For the same reason, I wouldn't hold my breath for a set-top Blu-ray recorder in North America anytime soon (despite the fact that they've long been available in Japan).
That's the [relatively] quick answer. But if I'm wrong, it certainly wouldn't be the first time. If anybody knows of a recorder with an HDMI input (or even a component input), let us known of your discovery by commenting below.
Note: This post has been updated to include a reference to older Philips and Sony DVD recorders that offered component video inputs (thanks, Wes#1 and Matt).